Before responding to the actual question, make sure that you read The Jurassic Park Effect where I talk about how "NAS OS" like FreeNAS, NAS4Free, OpenFiler and others are fundamentally a bad idea by being a bad product category that should never be considered outside of a lab (and one would question why you would use one there, but there are cases where it would make sense.)

Now the next set of issues is understand the concepts of the question. So let us start by defining what the question is about:

FreeNAS (and Similar) are NAS OSes. They are just a normal operating system with a web (or similar) interface added on to them for the purpose of managing the storage functions of the OS and hiding other functions. That's all. They are just an OS. It is just the software.

NAS is a hardware appliance that takes a server and a NAS OS and provides it as a single package of hardware and software with only an exposed interface for the storage functions (and necessary other configuration) and hiding most of the OS. That's all a NAS implies.

So the first issue with the question is that a NAS OS, or any OS for that matter, doesn't "have redundancy". Redundancy is handled in hardware, not software (for all intents and purposes.) So in both cases the software layer of FreeBSD and the software layer of any NAS both have zero redundancy. But a true NAS is not just software, so there might be redundancy.

The second issue is that since the term NAS implies nothing about the hardware but only that hardware and software are combined into a single product with a dedicated interface (e.g. an appliance) then we know nothing whatsoever about its redundancy. A high end NAS like NetApp or BluArc or Isilon or Exablox will have loads of redundancy options from controllers to RAID to RAIN to DR replication. But some NAS are nothing but a single laptop hard drive through into a little plastic box with a Raspberry Pi class board sharing out an SMB share with zero redundancy.

So even if FreeBSD or similar had some type of redundancy that we could measure, a NAS while on a specific case has redundancy (I can tell you the redundancy specifically of a ReadyNAS 312 in specific configurations, for example) as a general category does not. A NAS by virtue of being a NAS might have any amount of redundancy.

So neither side of the question that you asked about can we tell you what redundancy it may or may not have.

The same goes with performance. NAS OSes as a category and NAS as a category have no "performance." Imagine asking "how fast are desktops?" Well, they are the speed of the one that you choose to buy combined with how you have configured it. Same goes here.

We could, in theory, take a specific true NAS and compare its specific OS to a specific NAS OS like FreeNAS. In a case like that we could tell which is faster just at the software layer. But which will be faster overall is a factor of what specific hardware you decide to use for the NAS OS as well as how that specific NAS OS choice interacts with that specific hardware.

So what you care about always is reliability, not redundancy. There are reasons for discussing specific redundancy at a very granular, under the hood manner but exclusively for analyzing how it works for the purpose of determining the resulting reliability. The redundancy itself never matters, only how it impacts the resulting reliability. Reliability is always the goal regardless of how it is achieved.

Now that we have addressed the proximate question that was asked, I'll take a poke at what I believe your goal level question was meant to be.

I think that you are asking if you can build a file server (SAM-SD) that can compare to a standard NAS. And the answer is... of course. Once we know what a NAS is (Just a server with an operating system on it with a limiting interface) then we know from that alone that of course we can build our own server, put an OS on it and have something just as fast and reliable.

The trick, of course, is getting hardware that is as reliable than the NAS that we are considering and an OS that meets our needs.

The majority of NAS products in the SMB category are literally just taking stock servers (normally SuperMicro) and slapping Linux, FreeBSD or OpenSolaris on them, choosing software RAID and making a special management interface for customers to use that hide the majority of the OS from them.

The value to a NAS comes in being ready to use out of the box and the end to end support from the vendor.

Now high end NAS can have a lot of proprietary and "special sauce" ingredients that make them unique or special. Exablox OneBlox, for example, does proprietary RAIN and has really simple to use scalability. NetApp makes their own RAID level called RAID-DP (a dual parity version of RAID 4.) None of this really happens in the general SMB range of gear.

The original SAM-SD concept was developed to show that a $20K Red Hat Linux fileserver built on a stock HP Proliant DL585 could outperform a $500K NetApp for NFS sharing in a large cluster for a major bank. And it did, by a large degree in both performance and in reliability.

As a point of interest.... the TrueNAS NAS products are a traditional NAS and use FreeNAS as the OS on them. They use mid end server hardware (SuperMicro specifically), a NAS OS you would not normally consider for production use on its own, are based on an OS that is not considered good for storage and use software RAID.

You can easily build vastly better hardware, opt for hardware RAID if you want, get better support options (from vendors like HP, Dell and Fujitsu) and use a faster storage OS (like Linux or the Solaris family) for less money and beat the TrueNAS product in speed, reliability and cost.

The TrueNAS value is getting full vendor support from one vendor for the entire product. The downside is that you spend extra money getting less and it is almost impossible for a vendor like iX to provide the four or six hour response options and massive globally availability logistical supply chains of HP and Dell. TrueNAS is comparable to ReadyNAS or Synology in this case, so in that regards it is fine, when you have inclusive support.

If all that you need is two disks, then you will not be looking at building your own because there is no practical hardware for that on the market.

But if you are looking at consumer junk like D-Link, then why did you ask a question about performance and reliability? That does not fit. Your question would direct you in a different direction than your conclusion.

If you are looking at two bay NAS devices, your only reasonable options are ReadyNAS and Synology (or the ioSafe version of Synology.)

Now the next set of issues is understand the concepts of the question. So let us start by defining what the question is about:

FreeBSD (and Similar) are NAS OSes. They are just a normal operating system with a web (or similar) interface added on to them for the purpose of managing the storage functions of the OS and hiding other functions. That's all. They are just an OS. It is just the software.

NAS is a hardware appliance that takes a server and a NAS OS and provides it as a single package of hardware and software with only an exposed interface for the storage functions (and necessary other configuration) and hiding most of the OS. That's all a NAS implies.

i think you wanted to write FreeNAS instead of FreeBSD , a typo right ?

Now the next set of issues is understand the concepts of the question. So let us start by defining what the question is about:

FreeBSD (and Similar) are NAS OSes. They are just a normal operating system with a web (or similar) interface added on to them for the purpose of managing the storage functions of the OS and hiding other functions. That's all. They are just an OS. It is just the software.

NAS is a hardware appliance that takes a server and a NAS OS and provides it as a single package of hardware and software with only an exposed interface for the storage functions (and necessary other configuration) and hiding most of the OS. That's all a NAS implies.

i think you wanted to write FreeNAS instead of FreeBSD , a typo right ?

Looping back to this, in the past month I've worked with three different companies that all experienced significant data loss or downtime because of their choice of FreeNAS. Two suffered from not having front loaded their engineering and had an inability to support their servers during routine operations and caused major outages because of it along with significant cost for repairs, and one company that lost its data because of unnecessary bugs in the FreeNAS GUI code that would have been avoided has they been simply on FreeBSD.

Additionally this past week FreeNAS 10 "Coral" was demonstrated to be so incredibly unstable a month after being released that they had to recall the release and revert to a "beta" status indefinitely. For a trivial end user application this would be bad, for a critical storage infrastructure component on which companies need to have rock solid faith, it's unthinkable.